|Natarajan, Savithiry - Savi|
Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2006
Publication Date: 7/4/2006
Citation: Krishnan, H.B., Natarajan, S.S., Mahmoud, A.A., Bennett, J.O., Krishnan, A.H., Prasad, B.N. 2006. Assessment of indigenous nepalese soybean as a potential germplasm resource for improvement of protein in north american cultivars. Plant Science. 54:5489-5497. Interpretive Summary: Soybeans, which provide 67 percent of the vegetble protein and 30 percent of vegetable oil, are an integral link in the world food chain. Continued improvement in the performance of this crop is vital if increased demand for food by a burgeoning world population is to be met. Introduction of germplasm that has resulted from selection under different environmental conditions and food preferences holds potential for expanding the narrow genetic base of US soybeans. In this study, we have evaluated the potential of Nepalese cultivars for the improvement of protein quality. Nepalese cultivars contained significantly more protein and a higher concentration of specific essential amino acids than domestic cultivars. Results from this study indicate that the Nepalese cultivars hold potential for enhancing quality of domestic soybeans. These cultivars can be used by the breeders for the improvement of North American cultivars. Increased protein quality will benefit the overall utilization of soybean in the food and feed industries.
Technical Abstract: Soybeans contain approximately 35 percent protein and 20 percent oil, and represent an important source of protein in animal rations and human diets. Attempts are being made to increase further the overall protein content of soybeans by utilization of exotic germplasms. In this study, we have characterized soybean cultivars from Nepal and assessed their potential as a germplasm resource for improvement of protein content and quality of North American cultivars. Soybean cultivars “Sathia,” “Kavre,” “Soida Chiny,” indigenous to various regions of Nepal, contained 42 to 45 percent protein, which is significantly higher in comparison to that of the North American cultivar “Williams 82” (39 percent). Fractionation of seed protein by sodium dodecyl sulfate polyacrylamide gel electrophoresis and high-resolution two-dimensional gel electrophoresis revealed differences in the protein profiles of these cultivars. Various isoelectric forms of the glycinin and beta-conglycinin were identified by comparing the matrix-assisted laser desorption ionization time-of-flight mass fingerprinting data against the National Center for Biotechnology Information nonredundant database. Fluorescence two-dimensional difference gel electrophoresis analyses indicated that Sathia was distinct, lacking some isoelectric forms of acidic and basic glycinin subunits while expressing other unique forms. The contribution of these unique protein spots present in either Sathia or Williams 82 to the total protein content was quantified using scanning laser densitometry. Distinct restriction fragment length polymorphisms (RFLP) for Group-1 glycinin genes were observed among the tested Nepalese genotypes, indicating sequence variation among the cultivars. Conversely, evaluation of RFLP for the genes encoding Group-2 glycinins, beta-conglycinin and Bowman-Birk proteinase inhibitors indicated a high degree of conservation in these genes. Determination of amino acid composition, a reflection of protein quality, indicated that the arginine content of the Nepalese soybeans ranged from 7.7 to 8.1 percent, which was 5 to 10 percent higher than the 7.4 percent expressed in Williams 82. Additionally, Karve and Seti contained significantly more cysteine than Williams 82. The high protein content along with the desirable amino acid composition of the Nepalese soybean cultivars are traits that have potential for improving North American commercial cultivars.